JPH04236540A - Communication system - Google Patents

Abstract

PURPOSE:To realize the communication system in which lots of terminal equipment are simultaneously connected, a delay time is not increased, the terminal equipment is not expensive and the communication installation is efficient. CONSTITUTION:Terminal equipments 1A, 1B, 1C, 1D... and an exchange 2 directly connected to them or located closest to them are communicated by the synchronization transfer mode and the above exchange 2 and other exchange 3 in a network are communicated by the asynchronization transfer mode in the communication system having plural terminal equipment and plural exchanges.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system that combines a synchronous transfer mode method and an asynchronous transfer mode method.

0002

BACKGROUND OF THE INVENTION The development of communication technology in recent years has been remarkable. Traditionally, the main types of media that can be transmitted have been audio, text, graphics, and various data, but recently there has been an increasing demand for the transmission of still images and videos, and intensive research has been carried out in terms of exchange and transmission methods. Development is underway. The various media mentioned above have different amounts of information, and naturally have different transmission speeds. Therefore, conventionally,
Optimal line switching (first conventional example) or packet switching (second conventional example) is selected and used depending on the type of media to be transmitted and the transmission speed.

On the other hand, recently, digital network services that can handle various media in an integrated manner have been launched. This net is I
Integrated Services
Digital Network). Furthermore, ISDN is divided into narrowband ISDN (hereinafter abbreviated as N-ISDN) with a transmission rate of 1.5 Mbps or less, and
Broadband ISDN (hereinafter abbreviated as B-ISDN) of Mbps or higher.

[0004] One of the core technologies of B-ISDN is Asynchronous Trans, an asynchronous transfer mode that transfers fixed-length short packets called cells at high speed.
ferMode (hereinafter abbreviated as ATM) has recently
It is attracting attention worldwide. This ATM (third conventional example)
is a new communication system that can integrate and handle various media with different amounts of information on one network. The characteristics of ATM are that terminals with different communication speeds can be connected using the same line interface, so users do not need to be particularly conscious of communication speed, and that limited communication equipment can be used efficiently through statistical multiplexing. etc.

On the other hand, in ATM, all calls already connected to the network are statistically evaluated to have the specified service quality based on statistical information (maximum value, average value, etc. of transfer rate) declared by the terminal. The call will only be allowed to connect if it is satisfied. Therefore, compared to circuit switching, where connections are allowed if there is an available line, intelligent functions are required not only in the exchange but also in the terminal itself.

[0006]

[Problems to be Solved by the Invention] In the circuit switching of the first conventional example described above, once a terminal is allowed to connect, it permanently holds the line. Even if the line is not forwarded, other terminals cannot use the line. Therefore, this line switching has the disadvantage that the utilization efficiency of communication equipment such as lines and terminals is poor.

In the packet switching of the second conventional example described above, the line is not fixedly occupied by each individual terminal, and therefore the line utilization efficiency is improved, but as the number of connected terminals increases, the switching The problem is that the delay due to processing increases, making it unsuitable for communications that require real-time performance.

[0008] Furthermore, the above-mentioned third conventional ATM utilizes limited communication equipment as effectively as possible by using the statistical multiplexing effect, and therefore requires a high level of intelligence in the terminal. The problem is that it is expensive.

The communication system of the present invention has been developed with attention to the above points, and allows many terminals to be connected at the same time, without increasing delay time, without increasing the cost of the terminals, and improving the efficiency of communication equipment. The aim is to obtain a good communication system.

0010

[Means for Solving the Problems] The communication system of the present invention uses ATM and a synchronous transfer mode (Synchronized transfer mode) used for circuit switching and packet switching as transfer methods.
ous Transfer Mode Below, S
(abbreviated as TM). In addition, it focuses on the fact that the probability that multiple terminals connected to the network simultaneously transfer information at the maximum transfer rate is small, and accepts that there is a certain small probability that information will be discarded. Furthermore, the terminal is provided with a function to declare the maximum transfer rate for communication to the exchange, and the exchange is provided with means for extracting only valid information from the data transferred at a constant rate from the terminal. Furthermore, the network including the switching equipment monitors the actual traffic of the network and determines whether all calls can maintain the specified quality of service based on the maximum transfer rate declared by the terminal for call connection. Provide the function to do so. The above configuration achieves the above objective.

[0011]

Embodiment An embodiment of the communication system of the present invention will be described based on FIGS. 1 to 3. FIG. 1 is a schematic configuration diagram showing the basic part of an embodiment of the communication system of the present invention, FIG. 2 is a diagram showing changes in the amount of information with respect to unit time of the communication system shown in FIG. 1, and FIG. FIG. 3 is a diagram showing a transfer format of information transferred from the computer.

In FIG. 1, 1A, 1B, 1C, and 1D are communication terminals (hereinafter referred to as terminals) that comply with the network regulations.
They are installed in individual homes and businesses. There are more terminals, but they are omitted from the drawing. These are terminal 1A
, 1B, 1C, 1D, etc. include various types of terminals, such as those that perform voice calls, those that mainly communicate images, and those that support multimedia, but in the figure, they have the same configuration and are not implemented. Only necessary elements are shown in the explanation of the example. To explain this using terminal A (symbol 1A, hereinafter, the terminal code is shown in parentheses), as shown in the figure, there is a maximum transfer speed reporting unit 11A, which will be described later, and a transfer format assembly that assembles information into the transfer format shown in FIG. 3. Part 12A
, has a transmission path 6A and an interface section 13A for connection with the exchange 2, which will be described later.

[0013] In the figure, 2 is the switch closest to these terminals 1A, 1B, 1C, and 1D installed in the network, and is further connected to another switch 3 at the same or higher rank in the network. has been done. The configuration of a switch is generally complex, and again, only those elements necessary for the explanation of this embodiment are shown. That is, a valid information determining section 21, which will be described later, an ATM cell assembling section 22 for assembling ATM signals in a predetermined format, and interface sections 23A and 2 for interfacing with the terminals 1A, 1B, 1C, and 1D.
3B, 23C, 23D, and an interface section 24 for interfacing with a network management section 4, which will be described later.

In the figure, reference numeral 4 denotes a network management unit that grasps the amount of information provided within the network and determines whether or not the terminals 1A, 1B, 1C, and 1D are connected. This network management section 4 includes a status monitoring section 41 that constantly monitors the amount of information sent from the main transmission path 5, and uses an algorithm described later based on the data of this status monitoring section 41 to monitor these terminals. It has a determining section 42 that determines whether the connection is successful or not, and an interface section 43 that exchanges this determination with the exchange 2.

In the figure, reference numeral 5 denotes a trunk transmission line for transferring information between this exchange 2 and the exchange 3, and the signals transferred here are the above-mentioned ATM signals. Further, 6A, 6B, 6C, 6D are the terminals 1A, 1B, 1
This is a transmission line connecting C, 1D and this exchange 2, and the signal transferred here is the above-mentioned STM signal.

The network referred to in the present invention is a system including one or more of the above-mentioned exchange 2, exchange 3, network management section 4, trunk transmission line 5, and transmission lines 6A, 6B, 6C, and 6D. It is defined that a network including terminals 1A, 1B, 1C, 1D, etc. is a communication system.

Next, the operation of this embodiment will be explained. Terminal A (1A), terminal B (1B), and terminal C (1C) are
It is assumed that communication has already been performed with permission from the exchange 2 and the network management section 4 within the network. In addition, the transfer capacity per unit time of the main transmission line 5 is 20 (the unit is a slot, hereinafter omitted), and the terminal A (1A) is connected to the maximum transfer rate reporting section 1.
The maximum transfer rate per unit time reported by 1A is 7, terminal B (1B) is 5, and terminal C (1C) is 5. Here, the unit time is the basic time span set for network traffic management, and is used to determine the amount of effective information present within that time span and to manage the network and connect terminals. .

The basic unit of information transferred from each terminal 1A, 1B, 1C, 1D is each transfer format assembly section 12.
A, 12B, and 12C are assembled into a configuration in which a valid information flag is attached to the front of the information as shown in FIG. If the information is "absent", 0 is added as a valid information flag and transferred. In the figure, since the information is “present” for all 7 slots,
All valid information flags are 1. That is, the valid information determination unit 21 in the exchange 2 always
, 1C in the format shown in FIG. 3 via transmission lines 6A, 6B, and 6C, and its effective information amount is checked. The change in the amount of information shown in Figure 2 is
This is how it was obtained.

The status monitoring unit 41 in the network management unit 4 is connected to the valid information determination unit 21 and the ATM cell assembly unit 22 in the exchange 2.
The system constantly monitors changes in the effective information generated by the system, that is, the information transferred through the main transmission line 5 shown in (d) of the same figure.
The judgment unit 42 takes in this data, converts it into data, pools the amount of information for the most recent n units of time, performs calculations based on this, and uses the algorithm described later to determine whether a new communication call request is required.
Determine whether connection is possible. In this embodiment, 5 is adopted as the value of n.

[0020] Now, let us consider a case where a request for a communication call is generated from terminal D (1D). First, terminal A (1
The amount of information transferred per unit time for each of A), B (1B), and C (1C) is shown in FIGS. 2(a), (b), and (c). Each terminal A (1A) and terminal B via transmission lines 6A, 6B, and 6C
From the information sent from (1B) and C (1C), only valid information is extracted by the valid information discriminator 21 in the exchange 2, and only that valid information is sent to the trunk transmission line 5. In this case, the amount of effective information per unit time transferred through the trunk transmission line 5 is 1 for each, as shown in FIG.
It becomes 2, 11, 6, 16, 10.

The maximum transfer rate reporting unit 11D in the terminal D (1D) reports the maximum transfer rate 5 to the network management unit 4 via the transmission line 6D and the exchange 2. Through the operations described above, the network management section 4 takes into consideration the declared value (=5) and the transfer capacity of the trunk transmission line 5 described above, and determines whether or not the connection of this terminal D (1D) is successful.

[0022] Various algorithms can be considered for determining pass/fail, but the following two will be mentioned here. (1) The value obtained by subtracting the maximum value of the amount of information per unit time (16 in this example) in the most recent 5 unit times from the transfer capacity per unit time (20 in this example) of the main transmission line 5 ( 20-16=4) and the declared value of the terminal D (1D) (5 in this embodiment). In this case, this terminal D
Since the declared value of (1D) is larger, this terminal D (1D)
) is refused connection by the network management section 4.

(2) From the transfer capacity per unit time of the trunk transmission line 5 (20 in this embodiment), calculate the average value of the most recent information amount per unit time (referring to FIG. 2(d)). In the example, the value obtained by subtracting 11) (20-11=9) and this terminal D
The declared value (5 in this example) of (1D) is compared. In this embodiment, since the declared value of this terminal D (1D) is smaller, the network management unit 4 sends a connection enable signal to the exchange 2 and this terminal D (1D), and the communication path is subsequently set up. .

[0024] If the above algorithm (1) is adopted, although the number of terminals that can simultaneously participate in communication will be reduced, the amount of discarded information will be small. On the other hand, if the above algorithm (2) is adopted, although the number of terminals that can simultaneously participate in communication increases, the probability of the amount of information being discarded also increases. Each of these two algorithms has its own characteristics, and can be decided by taking into account the type of information, the way of thinking about the reliability of information, the cost of the system, etc. Other algorithms are also applicable.

In FIG. 1, the network management unit 4 is provided independently within the network, but it may also be included within the exchange 2.

As described above, in this embodiment,
Although there is a risk that the capacity of the main transmission line will be exceeded in a certain unit time and information will be discarded, by setting this risk to a small value, it will appear that the main transmission line will be A communication system is constructed that exceeds the communication capacity of the transmission line. In addition, the function added to the terminal is the declaration of the maximum transfer speed, which can be easily realized using the CPU installed in ordinary terminals, so it has the advantage that the cost of the terminal does not particularly increase. have

[0027]

[Effects of the Invention] The communication system of the present invention having the above configuration allows many terminals to be connected at the same time, does not increase delay time, makes the terminals simple and inexpensive, and improves the efficiency of communication equipment. It is possible to obtain a good communication system and has great industrial value.

[0028]

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing the basic parts of an embodiment of a communication system of the present invention.

FIG. 2 is a diagram showing changes in the amount of information with respect to unit time in the communication system shown in FIG. 1;

FIG. 3 is a diagram showing a transfer format of information transferred from a terminal.

[Explanation of symbols]

1A, 1B, 1C, 1D Terminals 11A, 11B, 11C, 11D Maximum transfer speed reporting unit (means to report the maximum transfer speed to the network) 2
Exchange 21 Valid information determination section (means for extracting only valid information) 3 Exchange (another exchange) 4 Network management section (means for determining whether to connect a terminal) 42 Judgment section (means for determining whether to connect a terminal or not) (means to judge)

Claims (2)

[Claims] Claim 1: In a communication system including a plurality of terminals and a plurality of exchanges, communication is performed between the terminal and the exchange directly connected to the terminal or the closest exchange using a synchronous transfer mode method, and the communication between the terminal and the exchange is A communication system characterized in that communication is performed using an asynchronous transfer mode method with other exchanges within a network. 2. The terminal has means for reporting a maximum transfer rate in the communication to the network when setting up a communication call,
The network including the switching equipment has means for extracting only valid information from data transferred at a constant rate from the terminal, and statistical data based on the maximum transfer rate or amount of effective information declared by the terminal. 2. The communication system according to claim 1, further comprising means for determining whether to connect or not.